An investigation into the suspected sexual abuse and exploitation of up to 20 children has been launched by police.

A 19-year-old man has been arrested and more arrests are expected as the inquiry into the suspected grooming of youngsters aged 12 and above gathers pace.

Devon and Cornwall Police said the alleged offences ranged from indecent assault to rape over a two to three-year period in the Torbay and Teignbridge areas.

Thousands of letters have been sent from Torbay Council to the parents of children at secondary schools telling them of the investigation.

Police said they had interviewed 20 children so far, who were mainly girls, from more than one school in the area.

Officers said the allegations did not involve paedophiles snatching children off the street and they stressed that the victims were known to the alleged offenders. The investigation is looking at whether social networking may have been involved.

At a press conference in Torbay, Detective Inspector Simon Snell, who is leading the inquiry, said there appeared to be "all manner of grooming taken place and it could well also be on the internet".

The suspect is being held at a police station in Torquay on suspicion of offences related to child exploitation. The inquiry started last week after children came forward to childcare agencies which then alerted police.

Mr Snell said: "We are looking at other people and other arrests may follow in the coming days and weeks."

Mr Snell said a team of 50 officers was working on the investigation and said the offences did not include prostitution.